Method of manufacturing electron tubes



Nov. 21, 1967 R. n n-:Goux

METHOD OF' MANUFACTURING ELECTRON TUBES 2 sheets-sheet 1 Filed Feb. 14, 1966 INVENTOR. RENE LEGOUX Nov. 21,1967 R. n r-:Goux

METHOD OF MANUFACTURING ELECTRON TUBES Filed Feb, 14, 1966 2 SheetS-Sheet 2 INVENTOR.

RENE' LEGoux AGL-nr United States Patent O ABSTRACT F THE DISCLOSURE A method of manufacturing an electron discharge tube having a photosensitive element in an evacuated discharge space formed by two portions of a tube envelope having grooved mating rim portions which are sealed together with a cold-welded soft material such as indium which seals the rims.

AThe invention relates to a method of manufacturing an electron tube havinga `photo-sensitive layer, whilst in the vacuum space in which the tube parts are degassed at a high'tempe'rature the'two parts of the tube envelope to be joined are held yat 'a given distance from each other, a photo-'sensitive layer is provided and the envelope parts concernedv are united to a closed tubeV by cold pressing, whilst the vacuum of the vacuum 'space is obviated and the ready tube is removed. Such a method is known for the manufacture of cascade image intensifying tubes not showing exhaust tube. It is completely carried out in a vacuum space. The tube parts are degassed therein and a photo-sensitive layer of the desired, frequently complex composition is applied by vapour deposition to a supporting body. After the supporting body, thus provided with a sensitive layer, which must not be exposed to the ambient atmosphere, is mounted in one of the envelope parts, the two tube parts are joined to each other (still in vacuo) by pressing the opposite rims with a great force one against the other. The material of these -rims is copper.

v`It has now been found that this method may be employed on a greater scale and can be made suitable particularly for the reproducible manufacture of photo-electric tubes, Vidicon tubes etc. by carrying out the invention, which is characterized in that one ofthe two envelope parts is provided with an uninterrupted edge, the upwardly orientated side of which is provided with a groove, whereas the other part has a corresponding edge, the downwardly orientated side of which has a prole suitable for cooperation with the first-mentioned edge, whilst during or after the degassing process for the various tube parts, when the tube parts are remote from each other, a mass introduced into said groove of soft material, preferably indium is melted, after which the parts are moved towards each other and away from each other so that the downwardly orientated edge of one of the tube parts is wetted by dipping in the bath of molten soft material in the groove of the other part, the parts being then cooled and the photo-sensitive layer being provided between the two parts of the tube envelope and linally the tube being closed bypressing the two envelope parts provided at their edges with a layer of soft material one against the other in the cold state.

It is thus proposed to wet one of the parts by ydipping it in a molten bath and to press the two parts with heavy force one against the other in one and the same vacuum space so that an intermolecular connection is established between the rims provided with a layer of soft solder.

It should be noted that it is known per se to introduce a material such as indium between the front plate and the adjacent part of a Vidicon tube and to establish a rm connection by using a compressive force between the two parts, in which case a high temperature is not required. The photo-sensitive layer, which should not be exposed to high temperatures, can then be applied to the front plate before the said parts are united to form a bulb. In this method the parts concerned are not wetted in vacuo and the connection between said parts is not established in vacuo.

It should furthermore be noted that it is also known to provide two parts in vacuo with an indium layer and to join them by cold pressing outside the vacuum space. The indium layer is applied by vapour deposition instead of by dipping in a bath, to the rims of the two parts to be joined. There is not applied a photo-sensitive layer in this case. l

In a preferred embodiment of the method according to the invention the upwardly orientated groove in the uninterrupted rim of one of the tube parts has the shape of a V and the corresponding rim of the other tube part a profile fitting in said groove.

The invention furthermore provides a particular method embodyingthis invention which is characterized in that in the position in which the tube parts partly covered with a layer of a soft material are remote from each other a number of vapour-deposition sources are arranged temporarily between said envelope parts and energized so that a supporting body in one of the tube parts can be provided with a photo-sensitive layer, after which said sources are removed from between the tube parts andthe tube is sealed.

In contrast to the conventional vapour-deposition techniques, in which the object is provided with a photosensitivelayer'at a stationary place remote from the tube, after which it is introduced between the tube parts to be united, no stationary furnace but a furnace movable in vacuo is employed in this method, which furnace is temporarily operative between the tube parts. A device suitable for carrying out this method, which comprises a vacuum bell to be exhausted which can be connected with a pump, means for holding the two envelope parts of an electronic tube at a given distance from each other, a furnace having vapour-deposition means for applying a photo-sensitive layer in vacuo to the supporting body which forms part of one of the envelope parts and means for pressing the facing rims of the envelope parts to be united in the cold state, is furthermore characterized in that the means for holding the envelope parts to be united serve to displace these parts with their facing rims only in a direction of height relatively to each other along a set of standing guide columns, and in that the device comprises furthermore means for moving the vapour-deposition furnace reciprocatorily in a lateral direction, which furnace is located in one of its positions at such a place between the envelope parts to be joined that the vapour-deposition means are just located opposite the supporting body to be covered.

The invention will be briey described with reference tional view of a vacuum bell inside which a photo-electric tube is manufactured.

FIGS. 2a and 2b are a longitudinal sectional and a cross-sectional view respectively of part of a vacuum bell inside which a photo-intensifying tube is manufactured and FIG. 3 shows the relatively co-operating closing rims of the two parts to be united of the envelope of an electronic tube.

The electronic tube to be manufactured by the method according to the invention is arranged in a vacuum space, the lower part of which has a body 1 of stainless steel, on which a glass bell is mounted. All members holding the various parts of the electronic tube and the members for moving said parts of various mechanisms to be moved in the vacuum space are connected with said body.

The vacuum in the bell 2 is obtained by means of a pump 5, which communicates through a metal valve 6 with the body 1. The various parts are intercoupled by suitable metal connections so that the vacuum exhibits a pressure of l-1 Torr.

The envelope of the electronic tube is formed by two cylindrical portions each having a metal ring 9 and 10 respectively, the facing rims of which rings are pressed one against the other under the action of a compressive force so that the envelope of the tube is sealed (see FIG. 3). The connection is established by pressing two parts against each other, which are covered with the same material, the yielding properties of which are favourablel Use is made of a soft metal. Among the suitable materials indium,y tin, lead, preferably indium is chosen. This metal is introduced into a V-shaped groove 9a of the lowermost part 9.

The downwardly orientated rim 10a of the uppermost part 10 is coated with the soft material by dipping this rim in a metal bath obtained by melting the material in the groove 9a. The parts 9a and 10a are previously cleaned preferably by etching and they may be coated with a gold layer of 1 to 2n thick.

The parts of the electroinic tube to be` manufactured are arranged inside the bell 2. The part forming the supporting body 11 of the photocathode is immovably held in the part 3, which part is supported from two columns 12. The associated envelope part 13 of the electronic l tube is secured to a block 14, which is displaceable along the columns 12. This block 14 is coupled with a rod 4 of a hydraulic press, which can provide a force of a few tons. The passage of the rod 4 through the wall of the vacuum space is of the conventional type so that a further description may be dispensed with.

The members containing the sources of the basic materials for the formation of the photo-sensitive layer(s) (for exam-ple Ag, Sb, Na, K, Rb, Cs) are also arranged inside the glass bell 2. These members are arranged preferably in a single group on a rotatable arm 1S. They are located in an auxiliary space 15 serving temporarily as a vapourdeposition furnace. These members are simultaneously displaced .by turning the arm 18. This arm is coupled by means of a lever and bellows system so that, when it is moved, the vacuum is maintained in the bell 2. Just before the formation of the photosensitive layer, the sources are arranged opposite the supporting body 11 to be coated and removed therefrom as soon as this layer is formed.

For this purpose the block 14 has first to be moved downwards so that the vapour-deposition device with the electrodes 19 is situated opposite the supporting body 11 for the sensitive layer.

When all members and the vapour-deposition furnace are arranged inside the glass bell 2, the bell is sealed in a vacuum-tight manner and the vacuum is produced inside the bell. Then thermal degassing is performed for the bell 2 itself, the various pump parts and all components of the electronic tube to be manufactured.

The vapour-deposition sources for the photo-sensitive layer are degassed at a temperature between 600y and 700 C. by heating with Joules heat. Also the indium in the groove 9a is then melted.

At the termination of the degassing process at a high temperature the block 14 is moved upwardly until the rim 10a is dipped in the molten indium bath in the groove 9a. The soft metal covers the metal rim 10a within a few minutes. Then the parts are moved away from each other and the temperature of the assembly is reduced to room temperature, the indium thus hardening.

The auxiliary space 15 with the various vapour-deposition sources is then moved in between the spaced envelope parts 9 and 10 by actuating the arms 18 so that the supporting body 11 forms the upper boundary of the auxiliary space 15; an opening of a few millimeters should, however, be left in the auxiliary space for pumping away unwanted gases developed by the various sources.

The materials which have to be evaporated at room temperature are first evaporated. Then the bell 2 and the tube parts are heated at a temperature which depends upon the nature of the photo-sensitive layer and may reach 250 C. This rise in temperature may be obtained by energizing a heating element 16.

After the termination of the physical-chemical formation of the photo-electric layer the temperature of the assembly is reduced to the ambient temperature of 30 to 40 C. This reduction may be accelerated by having a cooling liquid `circulating through a cooling pipe 17 inside the bell 2.

Finally the photo-electric tube is sealed. For this purpose first the auxiliary space 15 with the sources is tiltedl away into the position indicated in broken lines. inFIG. 2b. Then. the block 1'4 is moved upwardly by means of the rod 4 of the hydraulic press. The force exerted is of the order of l0 kga/mm. of the circumference ofthe rim (9, 10) and ensures a firm interconnection of the metallic, indium-coated surfaces.

Then the vacuum ofthe bell 2 may be obviated and the ready tube may be removed.

numerals. FIG. 2b shows the members for tilting away the f auxiliary space 15 into the position shown in broken lines.

FIG. 2a indicates by arrows the direction of vapourdeposition of one of the photo-sensitive materials (Sb). The electrodes for the diffuse distribution of alkali metals (Na, K, Rb) are designated by 19.

What is claimed is:

1. A method of manufacturing an electron discharge tube having a photo-sensitive layer in a vacuum space, in which the tube has parts which are degassed at a high temperature, two parts of the tube envelope to be joined being held at a given distance from each other, a photosensitive layer being provided and the envelope parts concerned being united to form a sealed tube by cold pressing, while the vacuum of the vacuum space is obviated and the ready tube is removed afterwards, characterized in that one of the two envelope parts is provided with an uninterrupted rim, the upwardly orientated side of which is provided with a groove, whereas the other part has a corresponding rim the downwardly orientated side of which has a profile suitable for co-operation with the first-mentioned rim, while the various tube parts are degassed, when the tube parts are remote from each other, a mass introduced into said groove consisting of soft material is melted, after which the parts are moved towards each other and away from each other so that the downwardly orientated rim of one of the tube parts is wetted by dipping in the bath of molten soft material in the groove of the other part, the parts being then cooled and the photo-sensitive layer being -provided between the two parts of the tube envelope and nally the tube being sealed by pressing the two envelope parts provided at their rims with a layer of soft material one against the other in the cold state.

Z. A method as claimed in claim 1, wherein the upwardly orientated groove in the uninterrupted rim of one of the two parts has the shape of a V and the corresponding rim of the other tube part has a profi-1e fitting in said groove.

3. A method as claimed in claim 2, wherein in the position in which the tube parts partly covered with a layer of a soft material are remote'from each other a number of vapour-deposition sources are arranged temporarily between said envelope parts and energized so that a supporting body in one of the tube parts can be provided with a photo-sensitivel layer, after which said sources are removed from between the two parts and the tube is sealed.

4. A method as claimed in claim 3 in which the soft material is indium.

No references cited.

10 RICHARD H. EANES, JR., Primary Examiner. 

1. A METHOD OF MANUFACTURING AN ELECTRON DISCHARGE TUBE HAVING A PHOTO-SENSITIVE LAYER IN A VACUUM SPACE, IN WHICH THE TUBE HAS PARTS WHICH ARE DEGASSED AT A HIGH TEMPERATURE, TWO PARTS OF THE TUBE ENVELOPE TO BE JOINED BEING HELD AT A GIVEN DISTANCE FROM EACH OTHER, A PHOTOSENSITIVE LAYER BEING PROVIDED AND THE ENVELOPE PARTS CONCERNED BEING UNITED TO FORM A SEALED TUBE BY COLD PRESSING, WHILE THE VACUUM OF THE VACUUM SPACE IS OBVIATED AND THE READY TUBE IS REMOVED AFTERWARDS, CHARACTERIZED IN THAT ONE OF THE TWO ENVELOPE PARTS IS PROVIDED WITH AN UNINTERRUPTED RIM, THE UPWARDLY ORIENTATED SIDE OF WHICH IS PROVIDED WITH A GROOVE, WHEREAS THE OTHER PART HAS A CORRESPONDING RIM THE DOWNWARDLY ORIENTATED SIDE OF WHICH HAS A PROFILE SUITABLE FOR CO-OPERATION WITH THE FIRST-MENTIONED RIM, WHILE THE VARIOUS TUBE PARTS ARE DEGASSED, WHEN THE TUBE PARTS ARE REMOTE FROM EACH OTHER, A MASS INTRODUCED INTO SAID GROOVE CONSISTING OF SOFT MATERIAL IS MELTED, AFTER WHICH THE PARTS ARE MOVED TOWARDS EACH OTHER AND AWAY FROM EACH OTHER SO THAT THE DOWNWARDLY ORIENTATED RIM OF ONE OF THE TUBE PARTS IS WETTED BY DIPPING IN THE BATH OF MOLTEN SOFT MATERIAL IN THE GROOVE OF THE OTHER PART, THE PARTS BEING THEN COOLED AND THE PHOTO-SENSITIVE LAYER BEING PROVIDED BETWEEN THE TWO PART OF THE TUBE ENVELOPE AND FINALLY THE TUBE BEING SEALED BY PRESSING THE TWO ENVELOPE PART PROVIDED THE THEIR RIMS WITH A LAYER OF SOFT MATERIAL ONE AGAINST THE OTHER IN THE COLD STATE. 